What is the initial workup and treatment for a patient suspected of having a pulmonary embolism (PE)?

Pulmonary Embolism Workup and Treatment

Begin immediate anticoagulation with weight-adjusted intravenous heparin (80 IU/kg bolus, then 18 IU/kg/hour) in patients with suspected PE while pursuing diagnostic confirmation through clinical probability assessment, D-dimer testing (if low-to-intermediate probability), and CT pulmonary angiography. 1

Initial Clinical Assessment

Recognize Classic Presentations

PE presents in three distinct patterns that should trigger immediate evaluation 2:

• Sudden collapse with elevated jugular venous pressure (hemodynamic instability)
• Pulmonary hemorrhage syndrome (pleuritic chest pain and/or hemoptysis)
• Isolated dyspnea (breathlessness without cough, sputum, or chest pain)

High-Risk Populations to Consider

PE is easily missed in three specific groups 2:

• Patients with severe pre-existing cardiorespiratory disease
• Elderly patients
• Patients presenting with isolated dyspnea only

Key Clinical Findings

Most patients with PE are breathless and/or tachypneic (respiratory rate >20/min) 2. Conversely, PE is rare in patients under age 40 without risk factors 2.

Step 1: Assess Clinical Probability

Major Risk Factors (Score +1 if present) 2:

• Recent immobilization or major surgery
• Recent lower limb trauma and/or surgery
• Clinical deep vein thrombosis
• Previous proven DVT or PE
• Pregnancy or postpartum period
• Major medical illness

Alternative Diagnoses (Score +1 if unlikely) 2:

• Other diagnoses are unlikely on clinical grounds
• Other diagnoses are unlikely after basic investigations (ECG, chest X-ray)

Step 2: Diagnostic Testing Strategy

For Low-to-Intermediate Clinical Probability

D-dimer testing is appropriate - a level <500 ng/mL excludes PE with posttest probability <1.85%, avoiding need for imaging 3. In patients aged ≥50 years with low probability, age-adjusted D-dimer thresholds can be used 3.

Very low-risk patients (age <50, heart rate <100/min, oxygen saturation >94%, no recent surgery/trauma, no prior VTE, no hemoptysis, no unilateral leg swelling, no estrogen use) require no further testing 3.

For High Clinical Probability (>40%)

Proceed directly to CT pulmonary angiography without D-dimer testing 3, 4. D-dimer is unnecessary and delays diagnosis 3.

Venous Compression Ultrasonography

Perform leg ultrasonography in conjunction with CT - positive findings confirm venous thromboembolism even if CT is negative 4. In one study, 55 patients had positive ultrasonography despite negative spiral CT 4.

Step 3: Immediate Anticoagulation

Hemodynamically Stable Patients (Systolic BP ≥90 mmHg)

Start weight-adjusted IV heparin immediately while awaiting diagnostic confirmation 1:

• Initial bolus: 80 IU/kg IV 1, 2
• Maintenance infusion: 18 IU/kg/hour continuous IV 1, 2
• Target aPTT: 1.5-2.5 times control (45-75 seconds) 1, 2

aPTT Monitoring Schedule 1, 2:

• First check: 4-6 hours after initial bolus
• After any dose change: 6-10 hours later
• Once therapeutic: Daily monitoring

Transition to oral anticoagulation once PE is confirmed 3:

• Direct oral anticoagulants (DOACs) are preferred over warfarin - apixaban, rivaroxaban, edoxaban, or dabigatran are noninferior for treating PE with 0.6% lower bleeding rates compared to heparin/warfarin 3
• For apixaban: 10 mg twice daily for 7 days, then 5 mg twice daily 5
• Continue heparin for minimum 5 days AND until INR ≥2.0 if using warfarin 2, 1

Hemodynamically Unstable Patients (Systolic BP <90 mmHg)

Systemic thrombolysis is recommended - associated with 1.6% absolute mortality reduction (from 3.9% to 2.3%) 3.

Do NOT use apixaban or other DOACs as initial therapy in hemodynamically unstable PE patients who may require thrombolysis 5. Unfractionated heparin is required 5.

Thrombolytic regimens 2:

• rtPA: 100 mg over 2 hours
• Streptokinase: 250,000 units over 20 minutes, then 100,000 units/hour for 24 hours (plus hydrocortisone)
• Urokinase: 4,400 IU/kg over 10 minutes, then 4,400 IU/kg/hour for 12 hours

Stop heparin before thrombolysis, then resume maintenance dosing afterward 2.

Patients Requiring Urgent Intervention

For patients with positive shock index (heart rate/systolic BP ≥1), perform urgent transthoracic echocardiography to assess right ventricular dysfunction and guide reperfusion decisions 6. This avoids time-consuming tests and prevents delays in life-saving therapy 6.

Common Pitfalls and Caveats

Do Not Miss These High-Risk Scenarios

• Patients with triple-positive antiphospholipid syndrome should NOT receive DOACs - use vitamin K antagonists instead due to increased thrombotic recurrence rates 5
• Patients with prosthetic heart valves should NOT receive apixaban - safety and efficacy not established 5
• Unexpectedly poor heparin response suggests pre-existing thrombophilia - may require higher doses 1

Monitoring Considerations

• Monitor platelet counts if heparin continues beyond 5 days due to heparin-induced thrombocytopenia risk 1
• Do NOT use PT, INR, aPTT, or anti-Xa levels to monitor DOAC effect - these tests are not useful 5

Duration of Anticoagulation

Minimum 3 months anticoagulation is required 7, 8. At 6-12 week follow-up 2:

• First episode with temporary risk factors: Consider stopping anticoagulation
• Idiopathic or recurrent PE: Consider indefinite anticoagulation and evaluate for thrombophilic disorders or occult malignancy 2, 7

Long-Term Follow-Up

Re-evaluate at 3-6 months for persistent symptoms to assess for chronic thromboembolic pulmonary hypertension (CTEPH) or post-PE syndrome 7, 8.